The biological optical measuring instrument is an instrument for obtaining information such as blood circulation, blood circulation dynamics and hemoglobin variation inside a living body by irradiating light having predetermined wavelengths into the living body and by measuring amount variation in light transmitted through the living body, in particular, a biological optical measuring instrument which is designed for obtaining blood stream information in a comparatively broad area in a form of a topography has been expected, for example, for a research of brain functions such as local center identification at the time of epilepsy stroke and clinical applications.
As an example of the clinical applications, a measurement result of hemoglobin variation in a brain at the time of performing motion and language task by utilizing a method called brain blood stream mapping method using near-infrared light is reported in WATANABE Eiju, “Brain Blood Stream Mapping Method Using Near-Infrared light” (CLINICAL NUEROSCIENCE Vol. 17, No. 11, 1999-11, P1280–1281, Cyugaiigakusya). In this method, in order to capture the hemoglobin variation in the brain, after performing a plurality of tests on respective tasks, averages of the respective values are calculated. This calculation of adding and averaging is performed for enhancing S/N ratio, because the hemoglobin variation in the brain, which is obtained through physiological stimulations such as the motion and language task, is at most about 5%.
In contrast to the fact that the amount of variation in optical signals due to hemoglobin, which is measured with these biological optical measurements, is in an order of a few percent, the amount of variation in optical signals caused by body movement reaches more than 50%, which is superposed in a spike like noise on an optical signal to be measured. Such a spike like noise can be separated by visual observation in a case of a single measurement data, which does not require the adding and averaging calculation, because such appears in a steep peak, however, in a case where the variation in the amount of hemoglobin is determined by the above referred to adding and averaging calculation, since the peak value due to the noise is averaged and is superposed on the measured data, it was difficult to separate the noise from the actual measured data, which has prevented accurate diagnosis.
In conventional biological optical measurements, in order to process measured data in which noises are contained, there were no methods other than a method in which the noises are recognized from the measured data through visual observation and a portion corresponding to the noises is removed from the result of the averaged hemoglobin amount variation, and of which method has been extremely impeded real-time data display property.
Accordingly, an object of the present invention is to provide a biological optical measuring instrument and a method thereof which permits to detect measured data containing noise components by utilizing a characteristic of the noise components which appear in steep peaks and to automatically remove through computation the optical signal portion containing the noise components from the measured result to be determined without relying upon the visual observation.
Further, another object of the present invention is to provide a biological optical measuring instrument and a method thereof which permits to quickly acquire highly reliable measurement result and thereby to provide valuable information for research and diagnosis.